On 05/26/2017 08:14 AM, Daniel Borkmann wrote:

On 05/26/2017 02:38 AM, David Daney wrote:

quoted

Since the eBPF machine has 64-bit registers, we only support this in
64-bit kernels.  As of the writing of this commit log test-bpf is 
showing:

   test_bpf: Summary: 316 PASSED, 0 FAILED, [308/308 JIT'ed]

All current test cases are successfully compiled.

Signed-off-by: David Daney <redacted>

Awesome work!

Did you also manage to run tools/testing/selftests/bpf/ fine with
the JIT enabled?

I haven't done that yet, I will before the next revision.

[...]

quoted

+struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
+{
+    struct jit_ctx ctx;
+    unsigned int alloc_size;
+
+    /* Only 64-bit kernel supports eBPF */
+    if (!IS_ENABLED(CONFIG_64BIT) || !bpf_jit_enable)

Isn't this already reflected by the following?

   select HAVE_EBPF_JIT if (64BIT && !CPU_MICROMIPS)

Not exactly.  The eBPF JIT is in the same file as the classic-BPF JIT, 
so when HAVE_EBPF_JIT is false this will indeed never be called.  But 
the kernel would otherwise contain all the JIT code.

By putting in !IS_ENABLED(CONFIG_64BIT) we allow gcc to eliminate all 
the dead code when compiling the JITs.

quoted

+        return prog;
+
+    memset(&ctx, 0, sizeof(ctx));
+
+    ctx.offsets = kcalloc(prog->len + 1, sizeof(*ctx.offsets), 
GFP_KERNEL);
+    if (ctx.offsets == NULL)
+        goto out;
+
+    ctx.reg_val_types = kcalloc(prog->len + 1, 
sizeof(*ctx.reg_val_types), GFP_KERNEL);
+    if (ctx.reg_val_types == NULL)
+        goto out;
+
+    ctx.skf = prog;
+
+    if (reg_val_propagate(&ctx))
+        goto out;
+
+    /* First pass discovers used resources */
+    if (build_int_body(&ctx))
+        goto out;
+
+    /* Second pass generates offsets */
+    ctx.idx = 0;
+    if (gen_int_prologue(&ctx))
+        goto out;
+    if (build_int_body(&ctx))
+        goto out;
+    if (build_int_epilogue(&ctx))
+        goto out;
+
+    alloc_size = 4 * ctx.idx;
+
+    ctx.target = module_alloc(alloc_size);

You would need to use bpf_jit_binary_alloc() like all other
eBPF JITs do, otherwise kallsyms of the JITed progs would
break.

OK, I was just copying code from the classic-BPF JIT in the same file. 
I will fix this.

quoted

+    if (ctx.target == NULL)
+        goto out;
+
+    /* Clean it */
+    memset(ctx.target, 0, alloc_size);
+
+    /* Third pass generates the code */
+    ctx.idx = 0;
+    if (gen_int_prologue(&ctx))
+        goto out;
+    if (build_int_body(&ctx))
+        goto out;
+    if (build_int_epilogue(&ctx))
+        goto out;
+    /* Update the icache */
+    flush_icache_range((ptr)ctx.target, (ptr)(ctx.target + ctx.idx));
+
+    if (bpf_jit_enable > 1)
+        /* Dump JIT code */
+        bpf_jit_dump(prog->len, alloc_size, 2, ctx.target);
+
+    prog->bpf_func = (void *)ctx.target;
+    prog->jited = 1;
+
+out:
+    kfree(ctx.offsets);
+    kfree(ctx.reg_val_types);
+
+    return prog;
+}